1. Field of Invention
The present invention relates to a piezoelectric oscillator including a piezoelectric resonator element and an oscillating circuit element to oscillate the piezoelectric resonator element, and a portable phone and an electronic apparatus employing the piezoelectric oscillator.
2. Description of Related Art
Piezoelectric oscillators are widely used in packages of small-sized information apparatuses, such as HDDs (Hard Disk Drives), mobile computers, and IC cards, or mobile communication apparatuses, such as portable phones, car phones, and paging systems.
A related art piezoelectric oscillator includes a piezoelectric vibrating unit having a piezoelectric resonator element and an oscillating circuit unit having an oscillating circuit element to oscillate the piezoelectric resonator element, and specifically a structure to house them in two different packages and fix the two packages.
In the structure to fix two packages to each other, a structure to superpose and fix two packages is known in the related art as a structure to mutually fix packages housing separate semiconductor elements, respectively. See Japanese Unexamined Utility Model Registration Application Publication No. 57-87544).
FIG. 32 is a schematic cross-sectional view illustrating such a semiconductor device 1. In the semiconductor device 1 shown in the figure, a first package 3 houses a first semiconductor element 4, and is covered with a cover 4a. A second package 2, on which the first package 3 is superposed, is a resin package, in which a second semiconductor element 6 is fixed to lead frames 5 and is molded out of resin 7. End portions of the lead frames 5 extend laterally and upwardly, and the end portions extending laterally are bent downward at the outside of the package to form mounting terminals 5a. The end portions of the lead frames 5 extending upwardly are exposed at a top surface of the second package 2 to form connection terminals 8.
The connection terminals 8 of the second package 2 are connected to external terminals 10 exposed at a bottom surface of the first package 3 by solder 9.
In this way, the first package 3 is electrically connected and bonded to the second package, and superposed on the second package 2.
This structure can avoid various disadvantages occurring when two kinds of semiconductor elements are housed in the same package.
That is, since two kinds of semiconductor elements are housed in a resin package, it is possible to avoid a disadvantage that the whole product cannot be used when any one of the semiconductor elements has defects. Specifically, in a case where it is intended to form a piezoelectric oscillator using a piezoelectric resonator element and an oscillating circuit element, not separate semiconductor elements, if they are housed in one package, gas generated in curing can be attached to the piezoelectric resonator element to cause deterioration of performance.
Therefore, similar to the aforementioned semiconductor device 1, these disadvantages can be avoided and a small-sized piezoelectric oscillator can be realized by housing the piezoelectric resonator element and the oscillating circuit element in separate packages, respectively and by superposing the packages vertically.
However, since a bottom surface of the first package 3 of the semiconductor device 1 is provided with the external terminals 10, its connection state to the second package is not visible from the outside, after the first package is connected and fixed to the second package 2.
Therefore, there is a problem in which a quality inspection, based on a product appearance, cannot be performed sufficiently.